Calefactio - Expansion Tank

The Calefactio HGT Series fixed-bladder expansion tank is designed to control thermal expansion and stabilize pressure in closed-loop hydronic heating, solar, and cooling systems. Its welded steel shell provides durable high-pressure construction, while the fixed EPDM bladder permanently separates system fluid from the tank’s air chamber to prevent waterlogging and internal shell contact. Factory pre-charged to 12 PSI, the tank can be adjusted during installation to match the system’s cold-fill pressure. Compatible with water and glycol solutions, the HGT-30 and HGT-60M provide reliable pressure management for boilers, radiant heating systems, hydronic distribution networks, and closed-loop HVAC installations.

Cross References

Calefactio — HGT-30: 4.8 gal fixed-bladder hydronic expansion tank

Calefactio — HGT-60M: 6 gal fixed-bladder hydronic expansion tank

Calefactio — HGT Series: Non-code expansion tank family for heating, solar, and cooling systems

Usage

The Calefactio HGT expansion tank is connected to a closed-loop hydronic system, normally near the boiler, air separator, or on the circulator’s suction side. As system water heats and expands, the additional volume enters the tank and compresses the air chamber behind the EPDM bladder. This limits pressure increases, reduces relief-valve discharge, and protects boilers, pumps, valves, and piping. Before installation, the tank must be isolated from system pressure and its air pre-charge adjusted to match the system’s cold static fill pressure. The tank is intended for non-potable heating and cooling circuits, not domestic drinking-water expansion control.